WELL FIRST OF ALL YOU DONT REALY HAVE ANY IDEA HOW EITHER OF THEM TRAINED.
Same goes for you. And you can tell if someone is training harder or not in comparison to another person. Go into a gym and watch an average person train and then see if you can spot a difference between their working out and the way an Olympic athlete works out. Does everyone train at the exact same level of intensity? Of course not.
Chris Lund has seen tons of bodybuilders train and he once remarked that if you combine Gaspari's intensity and Flex Wheeler's genetics, you'd get an unbeatable Olympia champion. Anyone who has seen Tom Platz train, knew he was a very intense guy. Nobody who saw Paul Dillett train (including other IFBB pros) raved about his intensity. In fact, Paul was known for his lazy training, light weights and sloppy form.
So some people DO train harder than others, just like some work harder than others, just like some study harder than others etc. It's a fact of life and just because you can't measure or judge it from a video or whatever doesn't mean it (the difference) doesn't exist.
And your saying "Intensity is not visible" is wrong - it should be, "Intensity isn't necessarily visible, at least in every case".
